(Of a triangle) having two sides of equal length.
- The base angles of an isosceles triangle are equal.
- Mathematicians sometimes say that A is an arbitrary isosceles triangle, but all they mean is that A could be any such triangle.
- First construct an isosceles triangle whose base angles are double the vertex angle.
Mid 16th century: via late Latin from Greek isoskelēs, from isos 'equal' + skelos 'leg'.
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